Friction disc for a false-twist device

ABSTRACT

Friction disc for a false-twist device, comprising an annular hub, on which it is possible to fix a circular race formed by a polyurethane (PU) layer and has a minimum wall thickness required for a secure interlocking fit, the hub having a circumferential support ring and a central hole, by which the friction disc is fixed on one of the shafts of the false-twist device. To ensure better dimensional and form stability over a long service life of the friction disc, the formed race fixed on the hub is ground according to a predefinable profile such that the flanks of the race have a predefinable width dimension following the grinding process, and/or in that the hub has, at a spacing from the support ring, a circumferential shoulder for abutment for the fixable PU layer, a cross-sectional width of the shoulder being smaller than a cross-sectional width of the support ring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from German National Patent Application No. DE 10 2019 112 892.7, filed May 16, 2019, entitled “Friktionsscheibe für eine Falschdrallvorrichtung”, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a friction disc for a false-twist device, comprising an annular hub, on which it is possible to fix a circular race that can be formed by a polyurethane (PU) layer and has a minimum wall thickness required for a secure interlocking fit, the hub having a circumferential support ring and a central hole, by means of which the friction disc can be fixed on one of the shafts of the false-twist device.

BACKGROUND OF THE INVENTION

In the context of producing crimped textile threads, it is known to generate a false twist on the threads that is introduced by friction and then set by means of thermal treatment of the threads, for example in a texturing zone.

To generate the false twist, false-twist devices in which the thread is guided along the circumferential surfaces of a plurality of rotating, overlapping friction discs during the twisting process have proven successful.

In such false-twist devices, as described for example in European Patent Publication EP 0 943 022 B1, the friction discs are generally arranged on three shafts, which in turn are rotatably supported in a bearing block. The shafts are arranged in a triangle, in each case spaced apart from one another, such that the friction discs overlap in the centre of the triangle. In addition, the shafts are driven by means of a drive in such a way that the friction discs rotate at a constant circumferential speed.

During the twisting process, while being acted upon frictionally the thread runs over the interacting friction discs at a relatively high conveying speed, said friction discs rotating at circumferential speeds of >2000 m/min. In the process, the frictional force between the thread and the friction discs circulating in a transverse plane to the thread running direction continuously generates the desired false twist.

However, the frictional stress leads to wear and tear on the friction discs, which is exacerbated by the friction discs heating up. To be able to guarantee a constantly good operating quality of a texturing machine equipped with false-twist devices, it should be ensured that the average deviation of the thread tension from position to position in the texturing machine is minimised. After a certain, often relatively short useful life, the friction discs of the false-twist devices must therefore be removed and replaced with new ones.

To keep the costs that arise during such overhaul work as low as possible, or to make the length of time between such overhaul work as long as possible, various proposals have already been presented in the past.

For example, U.S. Pat. Nos. 4,718,226 and 5,400,507 describe friction discs for false-twist devices, in which the aim is to keep the costs for overhaul work as low as possible by designing the race and the hub as separate components. In other words, in these known friction discs, the race, which is in frictional contact with the thread during the twisting process and is thus subject to wear and tear, can be exchanged for a new race as required, whilst the hub of the friction disc can continue to be used. However, the work required to exchange the race has proven to be impractical, so these friction discs have not become established in practice.

Additionally, German Patent Publication DE 35 00 208 A1 discloses friction discs in which the aim is to reduce the wear on the races by mixing a fine-powder substance with the rubber-elastic material of the races.

A similar friction disc is also described in German Patent Publication DE 10 2005 050 068 A1. According to that document, the friction discs each have a “liner carrier”, which is enclosed by a ring of frictional material. The frictional material is formed by a composite of a polyurethane and a ceramic material. In other words, ceramic nanoparticles are incorporated into a basic material made of polyurethane.

In these known friction discs, the service life of the friction discs was improved but to the detriment of the coefficient of friction, i.e. the coefficients of friction of these known friction discs leave lots of room for improvement.

Lastly, European Patent Publication EP 1 082 475 B1 discloses friction discs for which the manufacturing method is optimised by producing both the hub and the race by means of injection moulding technology. In other words, by means of an injection moulding method, a hub is initially produced from a hard thermoplastic and then a race is created on the hub likewise using an injection moulding method.

SUMMARY OF THE INVENTION

In this case, the race is formed by a layer of aram id-filled thermoplastic polyurethane (PU) that is mechanically fixed on the hub after the injection moulding process and has an almost identical, relatively thin layer thickness. Friction discs produced in this manner are comparably advantageous in terms of their manufacturing costs, but further improvements are certainly possible in terms of their service life and running properties.

Proceeding from the above-mentioned prior art, the problem addressed by the invention is that of improving the known friction discs of false-twist devices such that not only are they favorable in terms of production and have a relatively long service life, but also are very advantageous in terms of their running performance. In particular, the aim of the friction discs according to the invention is to minimize the generation of heat that is unavoidable during the false-twisting process.

According to the invention, the problem is solved, either alternatively or in combination, in that the race is ground according to a predefinable profile such that the flanks of the race have a predefinable width dimension following the grinding process and/or in that the hub has, at a spacing from the support ring, a circumferential shoulder for abutment for the fixable PU layer, a cross-sectional width of the shoulder being smaller than a cross-sectional width of the support ring.

Advantageous embodiments of the invention are set forth herein.

The embodiment according to the invention of a friction disc is particularly advantageous in that the friction disc is optimized in terms of its geometry and use of materials, as a result of which a considerably lower surface temperature can be produced during the texturing process due to the improved flow situation, which has a positive impact on both the running performance and the service life of the friction discs. In addition, the reduced temperature promotes energy savings when considered in relation to the number of friction discs on a spinning machine.

By means of the friction disc formed and precision-ground according to the invention, a considerably more stable machine cV % can be achieved, the “machine cV %” being understood as the average deviation of the thread tension from position to position of the texturing machine, as is known. This means that the lower and more uniform the machine cV % of a texturing machine, the better the quality of the yarn that can be produced on this textile machine, in particular in terms of later dyeing results of the yarn.

The defined formation of the circumferential shoulder ensures that advantageous flow conditions are constantly achievable in the region of the rotating friction disc, which also has a positive impact on the machine cV % during the texturing process. This is because a new hub shape that is improved compared with the hubs of previously known friction discs can ensure higher rigidity and strength, which also has a positive impact on a grinding process of the flanks of the race.

In addition, the new geometry of the hub of the friction disc leads to a larger surface area, the result of which is a lower disc temperature during the texturing process, which has a positive impact on the running performance and service life of the friction disc and can be used to increase the output of the texturing machine by increasing the rotational speeds of the friction discs.

In an advantageous embodiment, the width dimension of the flanks of the race is equal to, or more preferably is smaller than, the maximum cross-sectional width of the hub. Owing to a race wall thickness that can be provided to be comparably very thin as a result, it is possible, for example, to ensure that the swelling of the PU layer during the texturing process can be kept low, which leads to better dimensional and form stability, and thus to a lesser impact on the texturing process, throughout the service life of the friction disc.

Particularly preferably, according to one embodiment the wall thickness of the PU layer of the race is minimized to the minimum wall thickness required for the secure interlocking fit. The optimum minimization of the minimum wall thickness of the race achievable as a result not only allows the wear layer, in the form of the PU layer, to be securely adhered on the carrier, in the form of the hub, but also advantageously enables a further reduction of both the swelling of the PU layer and the surface temperature during the texturing process.

According to a further preferred embodiment, the hub is made of a plastic material, preferably of PBT 40% GK natural. PBT (polybutylene terephthalate) 40% GK natural is a thermoplastic that has a 40% glass-fiber content and is very well suited for the manufacture of machine components using an injection moulding method due to its favourable cooling and process performance. PBT is further distinguished on account of high strength and rigidity, very high dimensional stability and good resistance to friction and wear.

According to a further preferred embodiment, the PU layer of the race of the race of the friction disc has a hardness of at least or equal to 85 Shore A. A Shore hardness of this kind not only guarantees that the race has a relatively high resistance to wear, but also ensures that a sufficiently high resistance to friction is produced between the race and the yarn being processed, thereby guaranteeing that the yarn is false-twisted properly at all times during the texturing process.

The friction disc preferred according to any of the above-described embodiments also makes it possible to have improved air exchange between the ambient air that prevails between the adjacent friction discs during operation and heats up during the operation of the friction discs, and the cooler ambient air located outside of the friction discs.

According to a further preferred embodiment, the cooling action of the friction disc can be improved in that the hub has at least one passage through which the hub crosses in order to channel, in a predefined manner, the air flowing through the passage during rotational operation of the friction disc. By means of the passage, the two surface sides of the hub are therefore interconnected. The passage makes it possible to channel, in a predefined manner, an air stream, generated due to the rotation of the friction disc, of the entrained ambient air surrounding the hub, as a result of which the hub can be suitably cooled not only on the surface side but also along the profile thickness extending in the axial direction of the friction disc.

Preferably, the at least one passage is designed such that the air flowing through the passage during rotational operation of the friction disc leads towards an additional friction disc of the false-twist device arranged adjacently to the friction disc. As a result, it is possible to cool not only the friction disc itself, but also the adjacent friction disc. Different friction discs can therefore be used with a false-twist device, some having a cooling effect and some not having a cooling effect, said friction discs particularly preferably being arranged alternately along a shaft in order to achieve an improved cooling action.

Furthermore, the hub preferably forms a fan shape having a plurality of passages, which are separated from one another by a partition having a predetermined blade geometry for the defined channelling of the air flowing therethrough. Each partition, which separates two adjacent passages from one another, forms a fan blade for the defined channelling, through the respective passage, of the air stream generated from the entrained ambient air during the rotation of the friction disc. Preferably, at the end face arranged close to the central hole in the friction disc in the radial direction of the friction disc, each partition is immovably connected to the enclosure of the main body forming the central hole, and at the opposite end face in the radial direction, close to the support ring, each partition is connected to the portion of the main body carrying the support ring or alternatively to the circumferential shoulder spaced apart from the support ring. Each fan blade preferably has an aerodynamic profile, further preferably having a leading edge curved in the radial and/or axial direction of the friction disc and/or a trailing edge curved in the radial and/or axial direction of the friction disc. Further preferably, the number of the provided partitions is odd, five or seven partitions particularly preferably being provided and preferably being arranged evenly distributed in a circular manner around the central hole. Particularly preferably, the fan shape is selected to have the blade geometry such that the fan shape forms an axial or diagonal fan that entrains the ambient air from one side of the friction disc and blows it out on the other side of the friction disc in the axial direction of the friction disc or in the diagonal direction.

The fan shape according to any of the preferred embodiments has proven particularly advantageous for the cooling, and therefore for the service life of the false-twist device equipped with a friction disc of this kind. This is because the improved cooling action reduces the wear on the friction disc since the temperature-based chemical stress on the friction disc can be reduced during spinning preparation—the higher the temperature of the friction disc, the more rapid the chemical reactions on the friction disc associated with the spinning preparation, which cause increased wear on the friction disc. In addition, by providing friction discs having a cooling action, it is possible to omit an otherwise required external cooling air supply by means of, for example, separate blowers or the like that would need to be provided and which take up installation space.

According to a further preferred embodiment, the friction disc has a PU layer with a heat-conducting material, such as aluminium. A cooling action can thus likewise be achieved. In conjunction with the fan shape, the cooling action can be improved further.

According to a further aspect of the present invention, a false-twist device is proposed that comprises a bearing block having at least one rotatably mounted shaft that has at least two friction discs arranged along the shaft at a spacing from each other thereon, one of the friction discs, in particular the friction disc arranged the furthest away from the bearing block, being a friction disc having a cooling action according to any of the above preferred embodiments. Particularly preferably, the false-twist device has three shafts, each of which is rotatably supported and drivable in the bearing block. Further preferably, the shafts are arranged in a triangle, in each case spaced apart from one another, such that the friction discs arranged on the shafts overlap in the centre of the triangle. As a result, a self-cooling false-twist device having a longer service life can be provided.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention can be taken from an embodiment example presented below on the basis of the figures, in which:

FIG. 1 is a schematic perspective view of a false-twist device having a plurality of rotatably mounted shafts, on each of which three friction discs are fixed according to an embodiment example,

FIG. 2 is a plan view of the hub of a friction disc according to an embodiment example,

FIG. 3 shows the hub of a friction disc according to section B-B of FIG. 2,

FIG. 4 shows the hub of the friction disc according to section A-A of FIG. 2,

FIG. 5 is a section through a friction disc according to an embodiment example, comprising a hub of which the support ring is enclosed by a race formed by a PU layer,

FIG. 6 is a perspective view of a friction disc according to an embodiment example to approximately the original scale,

FIG. 7 is a section through a friction disc according to an embodiment example, comprising a hub designed in a fan shape, and

FIG. 8 is a schematic partially sectional view of a fan blade of the friction disc shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the embodiments of the present invention is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. The following description is provided herein solely by way of example for purposes of providing an enabling disclosure of the invention, but does not limit the scope or substance of the invention.

FIG. 1 is a schematic perspective view of an embodiment example of a false-twist device 1, as used, for example, in texturing machines in the context of the production of crimped textile threads 3.

As is known, false-twist devices 1 of this kind in each case have a bearing block 2 having a plurality of rotatably mounted shafts 4, which at their ends are connected to a drive (not depicted in FIG. 1). Drives of this kind for false-twist devices are known, however, and are described in relative detail in European Patent Publication EP 0 744 480 A1, for example.

As can also be seen in FIG. 1, the shafts 4, each of which is equipped with friction discs 5, are arranged such as to form a triangle. In the embodiment example, each of the shafts 4 has three friction discs 5 arranged one behind the other and spaced apart in the running direction F of the thread 3.

The exact configuration of a friction disc 5 according to an embodiment example is explained in greater detail below on the basis of FIGS. 2-6.

Each of FIGS. 2-4 shows a hub 6, made of plastic material, of a friction disc 5 according to an embodiment example to an enlarged scale and in different views.

As can be seen from FIG. 2, which is a plan view of a hub 6, the hubs 6 of such friction discs 5 each have an annular main body 13, which is created from a plastic material using an injection moulding method and has a central hole 8. The diameter of this central hole 8 is tailored to the diameter of the shafts 4 of the false-twist device 1, such that, once produced, friction discs 5 can be positioned on the shafts 4 of a false-twist device 1 without any problems.

As can also be seen, hubs 6 of this kind in each case have an outer, circular support ring 7 and a shoulder 11, which is likewise circumferential and is spaced apart from said support ring 7. In the main body 13 of the hub 6, a plurality of locking openings 12 (of which there are eighteen in the embodiment example) are also arranged between the support ring 7 and the shoulder 11. As explained below, these locking openings 12 are used to fix a race 9 (depicted in FIGS. 5 and 6) of the friction disc 5, said race consisting of a PU layer.

Each of FIGS. 3 and 4 is a section through the hub 6 of a friction disc 5. FIG. 3 shows the hub 6 according to section B-B of FIG. 2, whereas FIG. 4 depicts the hub 6 according to section A-A of FIG. 2.

As can be seen from FIGS. 3 and 4, the main body 13 of the hub 6 has its maximum cross-sectional width BN in the region of the central hole 8, whereas the cross-sectional width BS of the outer, circumferential support ring 7 of the hub 6 is slightly less than the maximum cross-sectional width BN of the hub 6.

In addition, the main body 13 of the hub 6 has a shoulder 11, which is likewise circumferential and is arranged at a spacing from the support ring 7, the cross-sectional width BA of said shoulder being slightly less than the cross-sectional width BS of the support ring 7.

As can be seen in particular from FIGS. 2 and 4, there are also a number (eighteen in the embodiment example) of so-called locking openings 12 arranged in the region between the support ring 7 and the shoulder 11, which locking openings make it possible to properly fix a race 9 (not depicted in FIGS. 2-4) made of PU in place.

FIG. 5 is a section through a finished friction disc 5 according to an embodiment example, i.e. a friction disc 5 having a hub 6 that is made from PBT using an injection moulding method and is enclosed by a race 9, which was also created in an injection molding method.

The race 9, which consists of a PU layer, encompasses the support ring 7, abuts the shoulder 11 and is ground according to a predefinable profile 14, has a substantially uniform, relatively thin profile thickness. In addition, the flanks 10 of the race 9 are ground to a predefined width dimension BFL in the region of the support ring 7. The width dimension BFL of the flanks 10 of the race 9 is slightly smaller than the maximum cross-sectional width BN of the hub 6.

FIG. 6 is a perspective view of a friction disc 5 according to an embodiment example to approximately a 1:1 scale. As already explained above, this friction disc 5 has a hub 6, made of a plastic material and having a central hole 8, and a race 9, which is likewise made of a plastic material. The hub 6, manufactured using an injection moulding method, advantageously consists of PBT (polybutylene terephthalate) 40% GK natural, whereas the race 9 consists of a PU layer which preferably has a hardness of at least or exactly 85 Shore A.

FIG. 7 is a section through a friction disc 5 according to a further preferred embodiment example, which is designed almost identically to the friction disc 5 according to FIG. 6, with the only difference being the configuration of the hub 6. Due to the identical configuration, marked by the same reference signs, reference is made to the above description.

The hub 6 according to this preferred embodiment example is formed as an axial fan, the main carrier portion between the central hole 8 and the shoulder 11 having a plurality of fan blades 15 arranged in a circular manner, in particular evenly distributed, around the central hole 8, said fan blades having an aerodynamic profile for the defined channelling of the ambient air from one side of the friction disc 5 to the other side. In this context, FIG. 8 is a schematic partially sectional view of a fan blade 15 of the friction disc 5 according to FIG. 7 in a perspective from the central hole 8 towards the support ring 11.

The friction disc 5 according to this preferred embodiment example promotes a cooling action of both the friction disc 5 and the false-twist device in which a friction disc 5 of this kind is used. For example, the friction disc 5 according to this embodiment example can be used in a false-twist device 1 shown in FIG. 1. In that case, it would be advantageous to arrange the friction disc 5 on the shaft 4 at the first position in the thread running direction F, i.e. at a position the furthest away from the bearing block 2 for the friction discs 5 to be arranged. Upon rotation of the friction disc 5 equipped with the hub 6 designed in a fan shape, an arrangement of that kind enables cooling in friction discs 5 arranged downstream in the thread running direction F, and in the bearing block 2 in which the drive for the shafts 4 can be housed. This has an advantageous impact on both the wear and the service life of the friction discs 5.

LIST OF REFERENCE SIGNS

-   -   1 False-twist device     -   2 Bearing block     -   3 Thread     -   4 Shaft     -   5 Friction disc     -   6 Hub     -   7 Support ring     -   8 Central hole     -   9 Race     -   10 Flank     -   11 Shoulder     -   12 Locking opening     -   13 Main body     -   14 Profile     -   15 Fan blade     -   F Thread running direction     -   BS Cross-sectional width/support ring     -   BFL Width dimension/flanks     -   BN Max. cross-sectional width/hub     -   BA Cross-sectional width/shoulder

It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements. 

What is claimed is:
 1. A friction disc for a false-twist device, comprising an annular hub, on which a circular race is fixable that is formed by a polyurethane (PU) layer and has a minimum wall thickness required for a secure interlocking fit, the hub having a circumferential support ring and a central hole, by which the friction disc is fixable on one of the shafts of the false-twist device, characterized in that the formed race fixed on the hub is ground according to a predefinable profile such that the flanks of the race have a predefinable width dimension following the grinding process; and/or the hub has, at a spacing from the support ring, a circumferential shoulder for abutment for the fixable PU layer, a cross-sectional width of the shoulder being smaller than a cross-sectional width of the support ring.
 2. The friction disc according to claim 1, characterized in that the width dimension of the flanks of the formed race fixed on the hub is equal to or smaller than the maximum cross-sectional width of the hub.
 3. The friction disc according to claim 2, characterized in that the wall thickness of the PU layer of the race is minimized to the minimum wall thickness required for the secure interlocking fit.
 4. The friction disc according to claim 1, characterized in that the hub is made of a plastic material.
 5. The friction disc according to claim 4, characterized in that the hub is made of polybutylene terephthalate (PBT).
 6. The friction disc according to claim 1, characterized in that the PU layer of the formed race fixed on the hub has a hardness of at least 85 Shore A.
 7. The friction disc according to claim 1, characterized in that the hub has at least one passage which passes through the hub in order to channel, in a predefined manner, the air flowing through the at least one passage during rotational operation of the friction disc.
 8. The friction disc according to claim 7, characterized in that the at least one passage is designed such that the air flowing through the at least one passage during rotational operation of the friction disc leads towards an additional friction disc of the false-twist device arranged adjacently to the friction disc.
 9. The friction disc according to claim 7, characterized in that the hub forms a fan shape having a plurality of passages, which are separated from one another by a partition having a predetermined blade geometry for the defined channeling of the air flowing therethrough.
 10. The friction disc according to claim 8, characterized in that the hub forms a fan shape having a plurality of passages, which are separated from one another by a partition having a predetermined blade geometry for the defined channelling of the air flowing therethrough.
 11. A false-twist device comprising a bearing block having at least one rotatably mounted shaft comprising at least two friction discs arranged along the shaft at a spacing from each other thereon, characterized in that one of the friction discs is a friction disc according claim
 8. 12. A false-twist device comprising a bearing block having at least one rotatably mounted shaft comprising at least two friction discs arranged along the shaft at a spacing from each other thereon, characterized in that one of the friction discs is a friction disc according to claim
 9. 